Circulating duct for boilers



June 23, 1931. H. H. PEEK ETAL 1,311,592

CIRCULATING DUCT FOR BOILERS Filed July 18, 19:0

Patented June 23, 1931 UNITED-STATES PATENT OFFICE.

HORACE H. PEEK AND LrnEUs c. GRIST, or GHATTANOOGA, TENNESSEE; SAID GRIST ASSIGNOR T0 SAID rEEK 1 cmc LAr'ING DUCT FOR nornnns Application filed July 18, 1930. 'Serial No. 468,903.

' This invention relates to water circulation constructions to aid the circulation of water in internal fired horizontal type boilers, and more particularly that :type of 5 boiler known as Scotch lmarineboilers, and comprises all-improvements over the prior art which are disclosedin this application.

One object is to provide a construction which will induce more rapid and more thorough circulation in the lower parts of the boiler with consequent increasedsteam generating quality of theboiler.

Other objects are to provide an improved mode of construction of water circulation ducts, and improved attachment of them to the furnace shell. I v p 1 1 The above and' other objects which will hereinafter appear, are attained by the new and useful improvements disclosedin this art to fully understand the essentialcharacteristics of the improvements drawings illustratlng certain ways .ofcarrying out the boiler with one form of the invention applied thereto.

Fig. 2 is a transverse section on line 2-2 ofFi'gzL, 1 p

Fig. 3 is a front elevation of one half. of a, modified form ofthe water circulating duct illustrated in Figs." 1 and 2.

Fig. 4 is a top plan view of Fig. 3.

Fig. 5 is a side elevation of Fig, 8.

Fig. 6 is a transverse sectional view on line 66 of Fig. 5

Fig. 7 is a view of a fragment of a furnace shell with modified attaching lugs thereon for attaching the halves of the water circulating duct illustrated in Figs. 3 to 6.

The type of boiler illustrated in Figs. 1 and 2 is known as a Scotch marine boiler. Within boiler shell 1 and spaced from the cylindrical wall thereof, is a cylindrical furnace shell 2 of furnace 3. Between shells 1 and 2 are fire tubes 4:. Between fire tubes 4: and furnace shell 2 are water circulating ducts 5.

application. To enable others skilledinthe Each water circulating duct 5 consists of two halves 6 having oppositely extending flanges or ears 7 connected to opposite sides of'flat upright lugs8 by bolts 9 passing through suitable holes in parts -7 and 8. Lugs 8 each have a semicircular cut out'portion 10 at their lowerends providing spaced feet 11 which are welded .to the top central portion of the furnace shell 2. Cut outs 10 result in less welding being needed and also tend to prevent accumulation of mud and scale about the base of the lugs 8. Each circulating duct half 6 has an auxiliary water circulation opening formed by openings 12 similar to corresponding openings 22 shown in Figs. 3 and 5. Openings 12 permit water to enter the ducts therethrough this water passingby the base of' the lugsx8 and preventing accumulation of sediment'about the lugs and consequently avoidingfoverheating of the furnace at these points. Each duct half 6 is channel-shaped in cross section as shell 2, and with the outer surface of. furnace shell 2 as one side,i thus forming a variable rectangular-in-cross-section water-circulation passage through each duct half 6. The outer surface 14 of each duct half 6 at its lower part extends straight down to near the inner surface of boiler shell 1 to form an enlarged duct-entrance opening 15 which large opening causes the waterto enter opening15 at low velocity and thus avoids lifting sludge and settlement usually lying on the bottom of a boiler. Beginning at the upper end of the straight outer portion of surfacel, the outer surface 14 follows a curve approximately concentric with :fur-

nace shell 2,' and then curves upwardly awaybelow the water level of the boiler and is pref:

erablyat a height intermediate of the top and bottom of a fire tube 4. of the top row. of fire tubes. By discharging the water at a point slightly below the level of the main body of water more rapid and desirable circulation is obtained. If the discharge were above the level of the main body of water in the boiler, there would be very little circulation as the water in the circulator would have to be converted into steam before being discharged and very little of the water in the boiler would be put into circulation. If the discharge were located just at the top of the furnace, the water would be discharged from the circulator into the large body of water above the furnace which would be comparatively inert and thus re-V tard the circulation of the water through the ducts.

In the ease of a smaller size boiler than shown in Figs. 1 and 2 having a lesser number of rows of fire tubes above the top of the furnace shell, the exit or discharge opening of the circulating duct would be nearer the top of the furnace shell, and'in such case a slightly modified construction is used as illustrated in Figs. 3 to 7. Attaching lugs 17 are similar in all respects to lugs 8 of Figs. 1 and 2 except that they are shorter and have only one bolt attaching hole 18. Correspondingly, modified circulating duct halves 19 have short ears 20 with single bolt holes 21. Openings 22 are the same as openings 12, and the shape and size of discharge opening formed by openings 23 of duct halves 19, is the same as the discharge opening 16 of Figs. 1 and 2.

One or more circulating ducts 5 may be placed in a boiler as shown in Fig. 1, and preferably with free space 24 at the ends of ducts 5 for a purpose to be described.

The portion of the furnace shell 2 above the grate level is subjected to the direct radiant heat of the fire. The water directly in contact with the upper portion of the furnace shell 2 and inside of the circulating ducts absorbs heat direct from shell 2, be

: comes of less density than the water more distant from shell 2, and whether with or without steam formed adjacent shell 2, this hot water tends to rise vertically upward, but is deflected by the outer surfaces 14 of 59 duct halves 6 and confined by end walls 13 so that it can only pass out discharge opening 16. The more distant cooler water descends on each side as indicated by arrows 25 and flows into the duct entrance openings 15 at the lower ends of the duct halves 6 to take the place of the hotter water rising within the duct. This newly entering water also becomes hot and rises up out of opening 16 and thus the circulation is continuous during operation of the boiler.

Under the bottom of the furnace 3 between points 26, the water tends to remain dormant and much lower in temperature than the water in the general circulation above the grate level, which causes slow circulation in the boiler and makes the boiler an unsatisfactory steamer and therefore inefficient. The circulation ducts herein disclosed in great measure overcome this sluggish circulation between points 26, and the circulation is still further improved by the free spaces 24 at the ends of the ducts. These end spaces 24 aid in causing circulation at 27 to take the place of water between points 26 which rises up into entrance openings 15.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention, and the present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim:

1. In combination, an internal fired horizontal type boiler having a furnace shell forming the outside of the furnace, and a boiler shell surrounding the furnace shell, lug means comprising a plurality of lugs, each lug having spaced legs attached to the furnace shell, and one or more water circulating ducts attached to the lug means.

2. In combination, an internal fired horizontal type boilerhaving a furnace shell forming the outside of the furnace, and a boiler shell surrounding the furnace shell, lugs attached to the top of the furnace shell, and one or more water circulating ducts attached to the lugs, each water circulating duct having an auxiliary water circulation opening adjacent the base of each lug to which it is attached.

3. The combination of claim 2 in which each auxiliary water circulation opening provides water circulation past opposite sides of the base of the adjacent lug.

In testimony whereof we affix our signatures.

HORACE H. PEEK. ALPHEUS C. GRIST. 

